An improved simulation of mesoscale dispersion of airborne cedar pollen using a flowering-time map

A model that simulates emission and dispersion of pollen of Japanese cedar (Cryptomeria japonica D. Don) was developed and tested for the Tohoku district of Japan. To fake into account the effect of altitude and local climate on flowering time, a flowering-time map was tested. The observed variation in the number of pollen grains was high in Yamagata City and relatively small in the southern cities. Sakata, facing the Sea of Japan, shows an individual pattern with two large peaks. Simulation without a flowering-time map predicted unobserved large peaks at the beginning and end of the cedar pollen season and tended to overestimate peaks in general. Simulation with a flowering-time map closely reproduced the changes in the number of airborne pollen grains with time at the beginning and end of the season and simulated the general variation in airborne pollen number well.